Add typed account and password settings

- Add admin account list, create, role, delete, and password workflows
- Execute identity-checked mutations through the existing dispatcher
- Bound queued credential lifetime and wipe transient secrets
- Add explicit password generation with saved-value acknowledgement
- Handle self-revocation and uncertain outcomes without automatic
  retries
- Register optional account routes without disrupting terminal
  transports
- Expand host regressions and document contracts and pending target
  checks

Validated host suites and pio run; hardware validation remains pending.

src/web_account_settings.h

@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-3.0-only */
+#pragma once
+#include <stdint.h>
+#include "esp_http_server.h"
+
+/* One session-bound pending/result slot. Dispatcher execution only; completed
+ * results are replaceable, not durable history or an idempotent retry API. */
+esp_err_t web_account_settings_handler(httpd_req_t *request);
+void web_account_settings_execute(uint32_t id);
+/* POST /api/settings/accounts/generate-password; bodyless admin cookie +
+ * Origin/CSRF. RNG only, no queued/account/persistent state or retrieval. */
+esp_err_t web_account_generate_password_handler(httpd_req_t *request);